Die separation, or singulation, by sawing is the process of cutting a microelectronic wafer or substrate into its individual circuit die with a mechanical rotating abrasive saw blade. As smaller and smaller microelectronic components are desired, wafer size is increased and thickness is reduced. As a result, the wafer becomes more fragile. Vibrations of the rotating abrasive saw blade are transmitted to the wafer and may cause significant chipping and/or micro-cracking in the wafer. Further, the vibrations can result in unacceptable cut quality and poor die-edge fracture strength. Additionally, higher performance, but more fragile wafer materials are increasingly used which also makes significant chipping and/or micro-cracking to the wafer more likely. The rotating abrasive saw blade is also susceptible to wear and blade clogging, which reduces the quality of die singulation over time.
Further, increasingly expensive materials are used for wafers. To reduce cost, increased die density on the wafer is desired. One effective way to achieve increased die density is to reduce street width or kerf of cut of the abrasive saw blade. However, reduction of blade width is limited by blade physical strength and useable life of the saw blade. Further, using very thin blades requires high rotation speeds to avoid undue vibration and frequent blade changes.
Singulation of a wafer using a laser rather than a mechanical saw is advantageous in many ways. For example, the laser does not transmit any mechanical stress to the wafer during cutting which reduces the likelihood of chipping and/or micro-cracking the wafer. Further, laser singulation is not susceptible to wear and blade clogging and has no consumable parts (i.e., saw blades). Still further, higher throughput and thinner, more accurate, singulation may be accomplished using a laser versus a mechanical saw.
However, the cost of ownership of a laser cutting system is substantially higher than that of a mechanical cutting system. As such, in many applications the aforementioned advantages of a laser cutting system do not outweigh the higher cost of ownership of the laser cutting system. To increase the attractiveness of a laser cutting system, the cost of ownership of a laser cutting system needs to be reduced.